Understanding the Biomechanics of Brain Injury in Combat

Biomechanical Explanations Were Missed by Myers

Previous parts in this series have focused on the contrast between the quality of the meticulous description of history and symptoms by Charles Myers’ in his seminal 1915 Lancet paper on “Shell Shock” and his clearly flawed “comment” that these case studies were explained by “hysteria.” The previous post focused on how Myers documented, but didn’t find significant, the loss of taste and smell. This blog will focus on the biomechanics of brain injury and the clues to the proper diagnosis, found in Myers’ detailed descriptions.

According to Myers, Soldier #1 was injured when he was surrounded by exploding shells, while he was caught in barbed wire. Soldier #2 was injured when the trench that he was taking cover in was imploded by an exploding shell and Patient #3 was injured when he was knocked 15 feet off a pile of bricks, by another shell. What could clearly have accounted for Myers’ misdiagnosis in these three cases studies was absence of evidence of a clear blow to the head from a shell in any of the above case studies. As is shown by other British research at the time, the head injury focus was with soldiers who suffered skull fracture.

It is now a known medical fact, that a direct blow to the head is not necessary for the brain to be injured in a traumatic event. Known biomechanical forces capable of causing of brain injury were directed to all three of these soldiers. Those biomechanics of brain injury include blast phenomenon, indirect blows to the head from either falls or flying objects, and acceleration/deceleration injuries.

Blast Injury Creates the Biomechanics of Brain Injury

When an explosion occurs, shock waves are generated that can penetrate the human body. Such shock waves can directly injure the brain and/or force the brain into the skull, injuring the brain as a result of such collision. Blast injury can injure, not just at the receiving end of the blast, but also at the firing end. One historic perspective of military medicine is that sailors who fired guns below deck, would over time show evidence of shell shock and dementia. See http://www.research.va.gov/news/features/blasts.cfm for research as to the direct effect of blast force waves on the brain. All three of Myers’ soldiers could have been injured by shock waves directly from blasts.

Biomechanics of Brain Injury Can Come from Blows to the Head.

The perfect example of an indirect blow to the head in Myers story is Soldier #3 who was knocked down from a height of 15 feet by the force of the blast. In the fall, such soldier clearly could have hit his head. Similarly, at the time that Soldier #2’s trench imploded on him, he could have been either knocked to the ground (striking his head) or some portion of the trench, or some object within it, could have hit him the head. While there is no direct details of a fall or a flying object in Soldier #1’s case study, such could also have occurred. A fall – especially one propelled by a blast – is one of the clearest understood mechanisms of injury. Not only is the force of the body being rapidly transferred to the head at the time of the fall, but the brain bounces inside the skull in reaction of the striking of the head.

In a slightly different mechanism, the force of a flying object is transferred to the brain, through the mechanism of a force wave, when the head is hit by an object. There is no way a biomechanical analysis of what happened to these three soldiers could have ruled out a mechanism of injury from an either a direct or indirect blow to the head. Clearly, Myers’ didn’t believe that any such blows to the head were sufficient to leave any substantial injury to the brain. In all likelihood, his ignorance of the biomechanics of brain injury explained his misdiagnosis.

Acceleration/Deceleration Injury to the Brain.

Without a doubt, all three of these soldiers head and necks were exposed to severe whiplash forces. Even without a blow to the head, such forces could be sufficient to injure the brain. Such injury can occur through at least two mechanisms: the collision between the brain and the skull or through the mechanism of diffuse axonal injury.

In a whiplash mechanism, especially one where a soldier is knocked down or falls, the brain and skull are accelerated at different speeds. When such occurs, there is a collision between the brain and the skull. See

In a diffuse axonal injury, it is not just that the brain is moving at relatively different speeds than the skull, but that different layers of the brain, are moving at different speeds from each other. This occurs because all human acceleration is angular, not linear. This means that rather than going in a straight line, the brain matter rotates on the radius of a circle. Layers of the brain have different densities and different distances from the fulcrum of the acceleration. This means that there is significant torque between these different parts of the brain.

Axons are long are microscopically thin connective portions of neurons, that span across these different layers of density and rotations. At the points of the greatest internal differential acceleration, forces can be sufficient to begin to stretch and tear the axons. For more information on Diffuse axonal injury, see http://subtlebraininjury.com/

Hypoxic Injury Could Have Occurred from Lack of Oxygen

One side note, in addition to these three potential mechanisms of injury, Soldier #2 could have suffered a hypoxic injury as a result of being buried in the trench. Hypoxia is when the brain or other organ, doesn’t get enough oxygen or blood flow to sustain itself. It is possible he did not receive enough oxygen during such period, resulting in brain damage.

It is odd that Myers would not have appreciated the potential for injury in the fall mechanism, especially with Soldier #3. But he can certainly not be criticized for his failure to recognize the potential for other injuries occurring without a direct impact to the head. Yet that flaw, whether excusable or not, makes his conclusion with respect to hysteria, completely dismissible. It is essential that current brain injury diagnosis exercise any lingering use of the hysterical or conversion diagnosis.

In our next part, we will look at the emotional issues that existed both before and after the injuries to these soldiers, and the role the wrong diagnosis, over emphasized the role of pre-injury emotional factors.

Attorney Gordon Johnson is one of the nations leading brain injury advocates. He is Past-Chair of the TBILG, a national group of more than 150 brain injury advocates. He has spoken at numerous brain injury seminars and is the author of the most read brain injury web pages on the internet, including http://waiting.com and http://tbilaw.com When Attorney Johnson talks about "recovery", he isn't talking about what a survivor recovers in litigation, but about getting better from a brain injury.For more information visit http://gordonjohnson.com

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